Protein kinase C (PKC) is a family of calcium stimulant and phospholipid-dependent serine/threonine -specific protein kinases which play an important role in cellular growth control, regulation, and differentiation. Protein kinase C is also fundamental to the processes involved in tumorigenicity, since it is the major high-affinity receptor for several classes tumor promoters as well as for endogenous cellular diacylglycerols. These tumor promoters also stimulate protein kinase C catalysis. Castagna et al., Biol. Chem. 257: 7847, 1982, reported direct activation of protein kinase C by tumor promoting phorbol esters. The mechanisms of protein kinase C action have been described in U.S. Pat. No. 4,816,450 issued Mar. 28, 1989 to Bell et al., the disclosure of which is incorporated as fully set forth herein. Protein kinase C is activated by diacylglycerol (DAG), a neutral lipid, and when activated will transfer the .gamma.-phosphate of MgATP to a serine or threonine residue on a substrate protein.
Since the activation of protein kinase C has been implicated in several human disease processes, including cancer tumors, inflammation, and reperfusion injury, inhibition of protein kinase C activity should be of great therapeutic value in treating these conditions.
Certain protein kinase C inhibitors have been reported to potentiate the antitumor activity of cis-platin both in vitro and in vivo. See Grunicke et al., Adv. Enzyme Regul. 28: 201, 1989 and German Offenlegungsschrift DE 3827974. In addition, it has been suggested that protein kinase C would be a potential target for therapeutic design because of its central role in cell growth. See Tritton, T. R. and Hickman, J. A. Cancer Cells 2: 95-102, 1990.
Further, inflammation and reperfusion injury, particularly pertaining to cardiac injury, are common conditions for which there exists no definitive treatment despite extensive research, and appropriate treatments for these conditions are needed.
Certain protein kinase C inhibitors have been demonstrated to block platelet aggregation and release of neutrophil activating agents such as platelet activating factor, PAF. See Schachtele et al., Biochem. Biophy. Res. Commun. 151: 542, 1988; Hannun et al., J. Biol. Chem. 266: 13620, 1987; Yamada et al., Biochem. Pharmacol. 37: 1161, 1988. Ceratin protein kinase C inhibitors have also been shown to inhibit neutrophil activation, and chemotactic migration. See McIntyre et al., J. Biol Chem. 262: 15730, 1987; Lambreth et al., J. Biol. Chem. 263: 3818, 1988; Pittet et al., J. Biol. Chem. 262: 10072, 1987; and Gaudry et al., ImmunoIogy 63: 715, 1988. Further, certain protein kinase C inhibitors have also been shown to inhibit neutrophil degranulation and release of proteolytic enzymes and reactive oxygen intermediates. See Wilson et al., J. Biol. Chem. : 12616, 1986; Fujita et al., Biochem. Pharmacol. 35: 4555, 1986; Berkow et al., J. Leukoc., Biol. 41: 441, 1987; Salzer et al., Biochem. Biophys. Res. Commun. 148: 747, 1987; Kramer et al., J. Biol. Chem. 262: 5876, 1989; and Dewald et al., Biochem. J. : 879, 1989. It is apparent that inhibitors of protein kinase C activity have the capability of blocking all three of the most significant mechanisms of pathogenesis associated with myocardial reperfusion injury, and should thus have a decided therapeutic advantage. Additionally, the inhibitory effect of protein kinase C inhibitors on keratinocytes, and on the oxidative burst in neutrophils will lead to an anti-inflammatory effect.
German Offenlegungsschrift DE 3827974 A1 discloses therapeutic preparations comprising a protein kinase C inhibitor in combination with a lipid, a lipid analogue, a cytostatic agent or phospholipase inhibitor useful for cancer therapy. However, none of the protein kinase C inhibitors disclosed in this publication is a furo-coumarinsulfonamide derivative.
Psoralen, a furo-coumarin, has been used for many years as an antipsoriatic agent in conjunction with light treatment. See Brokke and Christensen, J. Org. Chem. 24: 523, 1959; Anderson and Voorhees, Ann. Rev. Pharmacol. ToxicoI. 20: 235, 1980. Additionally, modified oligonucleotides containing a psoralen moiety have been disclosed as antiviral agents. See Weickmann, et al., Offenlegungsschrift DE 3928900A1.